A composite fibre has been known as a conjugate fibre formed by simultaneously extruding two kinds of spinning solutions from a single spinning nozzle having a partition provided therein to provide a spinning, and laminating together two kinds of fibres to form a single fibre.
Also has been known a melt composite spinning formed by using two kinds of thermoplastic resins different in a melting point from each other, for example, crystalline polypropylene (m.p. 165.degree. C.) as a high melting point polymer and polyethylene (m.p. 125.degree. C.) as a low melting point polymer, and simultaneously extruding both the resins in their melted state from a single spinning nozzle to form a single fibre.
In these conventional composite fibres, a spinning nozzle is used to effect spinning, and therefore, composite fibres obtained therefrom are limited to those of two component systems, and it has been extremely difficult to obtain composite fibres above three component systems.
Moreover, in the aforementioned melt composite spinning, two kinds of polymers are made into a composite form in the state of a concentric circle or an eccentric circle, and in the case where they are made into a composite form with a low melting point polymer positioned externally and a high melting point polymer, the low melting point polymer is melted so that fibres may be thermally bonded with each other. For example, after a web has been formed, the low melting point polymer is melted but when the high melting point polymer is subjected to heat treatment at a temperature at which it is not melted, contact parts of the fibres become fused, resulting in non-woven fabrics or the like. This non-woven fabric eliminates the necessity of a binder such as a synthetic rubber emulsion, and therefore has an advantage that various disadvantages caused by the use of the binder may be avoided.
However, in the above-described melt composite spinning, dies, nozzles and the like are complicated in construction, and for this reason, the composite fibres above three component systems may not only be obtained but thermoplastic resins used therefor are limited to polymers which can be thermally welded with each other.
Furthermore, even in the composite fibres comprising two component systems, since it is difficult to change color of raw material, a colored non-woven fabric as a final product is hard to obtain. Despite the possession of characteristic of thermal adhesion, the range of utilization thereof bas been greatly limited.
A problem encountered in the conventional composite fibres lies in carrying out the composition of fibres at the time of spinning. From a viewpoint that the aforesaid problem is solved if the composition is carried out by other means, the present inventors have repeatedly studided on the composition of fibres by means other than spinning.